When Grady's family moves out of the city and into an old house in Fever Swamp, both he and his sister, Emily, find a lot wrong - they have no friends, no neighbors and nothing to do. Then Grady meets the only other kid around, Will, who tells him the legend of the swamp and about the werewolf responsible for the mysterious disappearances of many former residents. Although Grady is afraid the legend may be true, his parents and sister don't, that is until the next full moon.